docs: def com_google_fonts_check_fstype(ttFont):
    """Checking OS/2 fsType.
  
    Fonts must have their fsType field set to zero.
    This setting is known as Installable Embedding, meaning
    that none of the DRM restrictions are enabled on the fonts.
  
    More info available at:
    https://docs.microsoft.com/en-us/typography/opentype/spec/os2#fstype
    """
    value = ttFont['OS/2'].fsType
    if value != 0:
      FSTYPE_RESTRICTIONS = {
        0x0002: ("* The font must not be modified, embedded or exchanged in"
                 " any manner without first obtaining permission of"
                 " the legal owner."),
        0x0004: ("The font may be embedded, and temporarily loaded on the"
                 " remote system, but documents that use it must"
                 " not be editable."),
        0x0008: ("The font may be embedded but must only be installed"
                 " temporarily on other systems."),
        0x0100: ("The font may not be subsetted prior to embedding."),
        0x0200: ("Only bitmaps contained in the font may be embedded."
                 " No outline data may be embedded.")
      }
      restrictions = ""
      for bit_mask in FSTYPE_RESTRICTIONS.keys():
        if value & bit_mask:
          restrictions += FSTYPE_RESTRICTIONS[bit_mask]
  
      if value & 0b1111110011110001:
        restrictions += ("* There are reserved bits set,"
                         " which indicates an invalid setting.")
  
      yield FAIL, ("OS/2 fsType is a legacy DRM-related field.\n"
                   "In this font it is set to {} meaning that:\n"
                   "{}\n"
                   "No such DRM restrictions can be enabled on the"
                   " Google Fonts collection, so the fsType field"
                   " must be set to zero (Installable Embedding) instead.\n"
                   "Fonts with this setting indicate that they may be embedded"
                   " and permanently installed on the remote system"
                   " by an application.\n\n"
                   " More detailed info is available at:\n"
                   " https://docs.microsoft.com/en-us"
                   "/typography/opentype/spec/os2#fstype"
                   "").format(value, restrictions)
    else:
      yield PASS, ("OS/2 fsType is properly set to zero.")